The present invention relates to volumetric displays. More specifically, but without limitation thereto, the present invention relates to a rotating projection screen for a three-dimensional volumetric display.
3-D display technologies such as holography, stereoscopic displays, and advanced 3-D graphics engines generally render 3-D images as a two-dimensional display by mapping the coordinates of the 3-D images into 2-D perspective. However, these technologies lack the physiological depth cues needed for true 3-D display imaging, such as motion parallax, accommodation, convergence, and binocular disparity. A 3-D volumetric display provides the physiological depth cues needed for such applications as automotive design, architecture, and medical imaging.
One method for displaying a three-dimensional image is to illuminate a series of points on a two-dimensional surface as it sweeps out a volume with a periodic motion. In FIG. 1, a 3-D volumetric display 10 of the prior art comprises beam deflector control circuit 102, beam deflectors 104, 106, and 108, mirrors 110, a display surface 120, and a drive motor 130. In this example, display surface 120 is implemented as a double helix, although other surface geometries may also be used, such as a single helix, a multiple helix, a piston, etc. Drive motor 130 imparts a periodic motion to display surface 120 within a display volume 122. Beam deflector control circuit 102 inputs world coordinates of a scene and causes beam deflectors 104, 106, and 108 to direct light beams 116 onto display surface 120 from mirrors 110. Light beams 116 illuminate view coordinates on display surface 120 to generate an image representative of the scene corresponding to the input world coordinates. The motion of display surface 120 scatters light from light beams 116 at different positions within display volume 122, time-multiplexing the illuminated view coordinates to generate a complete three-dimensional image to the eye of an observer 150. As long as the diameter of display surface 120 is within about three feet, a reasonably stable image may be obtained. For larger displays several feet in diameter, however, mechanical instability and irregularities in the propeller shape of display surface 120 can cause unacceptable jitter in the displayed image. Also, the air resistance of a spinning large surface causes noisy operation.
A need therefore exists for a volumetric display that can be scaled up to a suitable size for automotive and medical applications.